Engine anti-diesel and deceleration control

ABSTRACT

The throttle valve of a downdraft type carburetor is controlled in its movement by a servo in turn controlled by manifold vacuum changes; servo springs initially move the throttle valve to a closed position for engine anti-dieseling; engine running vacuum moves the servo diaphragm to open the throttle valve to an idle speed position; and, engine decelerations effect a delayed throttle valve closing to reduce emissions.

United States Patent [191 Cedar Aug. 21, 1973 1 ENGINE ANTI-DIESEL ANDDECELERATION CONTROL [75] inventor: Raymond J. Cedar, Birmingham,

Mich.

[73] Assignee: Ford Motor Company, Dearbom,

Mich.

[22] Filed: Nov. 29, 1971 [21] Appl. No.: 202,913

[52] US. Cl... 123/198 DB, 123/D1G. 11, 123/97 B,123/103,123/1l9,123/179 G [51] Int. Cl. F02m 19/12, F02m l/l4, F02d33/00 [58] Field of Search 123/D1G. ll, 97 B, 123/198 D, 198 DB, 198 DC,179 86,179 G, 119,180 E, 103

[56] References Cited UNITED STATES PATENTS 3,618,582 11/1971 Gerlitz..123/198DB 1/1970 Bumia 123/198 DC X 9/1971 Sherwin 123/97 B PrimaryExaminer-Al Lawrence Smith Attorney-Keith L. Zerschling and Robert E.

McCollum [5 7] ABSTRACT The throttle valve of a downdraft typecarburetor is controlled in its movement by a servo in turn controlledby manifold vacuum changes; servo springs initially move the throttlevalve to a closed position for engine anti-dieseling; engine runningvacuum moves the servo diaphragm to open the throttle valve to an idlespeed position; and, engine decelerations effect a delayed throttlevalve closing to reduce emissions.

2 Claims, 1 Drawing Figure ENGINE ANTI-DIESEL AND DECELERATION CONTROLThis invention relates, in general, to a device for positioning thethrottle valve of a carburetor to minimize the emission of undesirableelements into the atmosphere. More particularly, it relates to a vacuumcontrolled servo to control fuel and air flow through a carburetor afterengine shutdown and during engine deceleration to prevent enginedieseling and minimize the passage of unburned hydrocarbons into theatmosphere.

The problem of engine dieseling after the engine has been shut off isrecognized. So long as the engine crankshaft continues to rotate, avacuum signal will be present in the carburetor throttle bore below thethrottle valve. This pulls idle system fuel and air into the hotcombustion chamber such that combustion is maintained for a few secondsor longer after the engine is shut off. This naturally is undesirable.Also, during engine deceleration, the very high manifold vacuumdeveloped not only draws excessive fuel from the idle system butinterferes with the proper scavenging of the exhaust gases from thecombustion chamber. This results in incomplete burning at this time,and, therefore, unburned hydrocarbons may pass out into the atmosphere.

ln the prior art devices, the minimum flow and engine idle speedpositions of the throttle valve usually are the same. Therefore, whenthe engine is shut off, the vacuum signal still present for a fewseconds draws a sufficient charge of fuel/air mixture into thecombustion chamber to maintain the engine running.

The invention eliminates the above problem by providing a servo toessentially close the throttle valve automatically upon engine shutdown;thereby reducing the charge of fuel/air mixture below the level neededto overcome the frictional resistance of the engine to sustain running.

The prior art devices also generally made no provision for overcomingthe induction of a rich charge of fuel/air mixture during deceleratingoperation, when the vacuum signal on the idle system is very high.

The invention again overcomes the above problem by the servo describedpreviously also automatically retarding the closing of the throttlevalve in response to deceleration, so that the increased air flow willdecrease the idle system fuel signal, will better scavenge thecombustion chambers of exhaust gases, and will maintain the air/fuelratio more in the range of a combustible mixture, all to decreaseemissions.

It is one of the objects of the invention, therefore, to provide acarburetor with a throttle valve positioner that will automaticallyposition the throttle valve for idle speed operations; will preventengine dieseling upon engine shutdown; and, will minimize the passage ofunburned hydrocarbons into the exhaust system or atmosphere duringengine decelerating operating conditions.

It is also an object of the invention to connect the throttle valve of acarburetor to a servo that is controlled by manifold vacuum that will attimes essentially close the throttle valve to reduce the flow of fueland air to the engine cylinders upon engine shutdown; will only slowlyclose the throttle valve when the engine is decelerating; or, willnormally position the throttle valve for idle speed running.

Other objects, features and advantages of the invention will become moreapparent upon reference to the succeeding detailed description thereof,and to the drawing illustrating a preferred embodiment thereof, whereinthe figure illustrates schematically a cross sectional view of a portionof a carburetor embodying the invention.

A portion 10 of a downdraft type carburetor is illustrated, although itwill be clear as the description proceeds that the invention is equallyapplicable to other types of carburetors, such as updraft or sidedraft,for example. More particularly, the carburetor is provided with a mainbody portion 12 having a cylindrical bore 14 providing the conventionalair/fuel induction passage 16. The latter is open at its upper end 18 toclean air at near atmospheric pressure that has, for example, passedthrough the conventional air cleaner, not shown. At its lower end 20,passage 16 is adapted to be connected to a conventional intake manifoldfrom which the air and fuel mixture passes to the engine cylinders, notshown, in a known manner.

The flow of air and fuel through induction passage 16 is controlled inthis instance by a conventional throttle valve 22. The latter is fixedon a shaft 24 mounted for rotation in the side walls of body 12, in aknown manner. A main fuel system is not shown, since it can be any ofmany known types. Suffice it to say that the fuel would be inducted intopassage 16 from above the throttle valve in a known manner as a functionof the rotation of the valve from its fully closed position 34 to a wideopen nearly vertical position, by the change in engine manifold vacuumsignal.

The carburetor also contains a conventional idle system for supplyingthe necessary fuel and air to the engine cylinders around the throttlevalve during engine idling and off idle speed operation. A bypasspassage or channel 26 contains the usual transfer port 28 and adischarge port 30 controlled by an adjustable needle valve 32.

The transfer port 28 is located so that its lower edge is aligned withthe edge of the throttle valve plate in its closed full line position34. Alternatively, if desired, the transfer port can be locatedvertically in other positions relative to the throttle plate edge whenthe latter is in the closed position. The dotted line position 36, onthe other hand, indicates the idle speed position of the throttle valve,while dotted line position 37 indicates a deceleration position, to bedescribed more fully later.

It will be clear that in the closed position 34, the idle passage areaexposed to the vacuum existing below the throttle valve is reduced fromthat when the throttle valve is in position 36. Therefore, a lowerquantity of fuel and air will flow at this time as the area of thetransfer port 32 above the throttle valve edges subjects passage 26 toan ambient or atmospheric pressure bleed. The quantity flowable past theneedle valve at this time, therefore, is selected to be insufficient toprovide the torque necessary to overcome the engine friction.

It will also be seen that when the throttle valve is positioned in itsidle speed dotted line position 36, the transfer port area subjected tothe vacuum signal below the throttle valve is increased so as toincrease the amount of fuel and air to pass through the idle system toan amount needed to maintain the engine at idling speed.

It will also be clear that when the throttle valve is in position 37,increased air flow will occur. This exists during deceleration, as willbe described more clearly, later. Portion 37 more efficiently scavengesthe combustion chambers of exhaust gases to minimize the passage of anyunburned fuel into the exhaust system and atmosphere during enginedecelerating operating conditions; it decreases the vacuum signal inidle passage 26; and, provides a more combustible mixture to the enginethan when closed.

To accomplish the above, a lever or link 38 is fixed on or formedintegral with the throttle valve shaft 24 for rotation with it, atension spring 40 biasing lever 38 in a counterclockwise direction atall times to bias the throttle valve towards its closed position.

The lever 38 is adapted to be moved clockwise to the right, as seen inthe Figure, by a servo 42 to rotate throttle valve 22 clockwise to itsengine idle speed position 36.

The servo comprises a hollow two-piece shell 44 with an annular flexiblediaphragm 46 clamped between. The diaphragm divides the shell into anatmospheric or ambient pressure chamber 48 and a vacuum chamber 50.Apertures 52 connect chamber 48 to the surrounding air. A tube 54connects chamber 50 to a manifold vacuum sensing port 56 in thecarburetor bore.

A sleeve 58 is sealingly clamped at one end to the diaphragm 46 andsealingly projects out through a hole 60 in the wall of shell 44. Theouter end of sleeve 58 is crimped inwardly to form an aperture 62through which a plunger 64 slides with a frictional fit. The plungerforms a part of a dashpot assembly including sleeve 58, and is adaptedto abut the throttle valve lever 38 to move, or be moved by the lever,as the case may be.

Plunger 64 is formed integral with a piston 66 that slides within sleeve58. A light spring 68 normally biases the piston and plunger 64outwardly against the lever 38. The spring 68, however, is lighter thanreturn spring 40, and cannot push the lever 38 to the right.

Piston 66 contains an air bleed 70 for communicating air only slowlybetween opposite sides of the piston. The frictional engagement ofsleeve 58 with plunger 64 is not so tight as to prevent the flow of airfrom the outside into the chamber 72 defined between the end of shell 38and piston 66. As stated previously, sleeve 58 is sealingly secured tothe diaphragm. Therefore, a close fit between piston 66 and sleeve 58provides an air chamber 74 for proper working of the dashpot, in amanner to be described.

Completing the construction, a spring 76 normally biases the diaphragm46 and sleeve 58 to the position shown, in the absence of vacuum inchamber 50.

In operation, when the engine is shut down, servo chambers 48 and 50 areat atmospheric or ambient pressure, and spring 76 has moved diaphragm 46to the free position shown. The throttle return spring 40, beingstronger than spring 68, has moved the throttle valve 22 to its closedposition 34, and moved plunger 64 to the position shown, partiallycollapsing spring 68.

The engine now would be started by the operator partially depressing theaccelerator pedal, in hot weather, or partially depressing and releasingthe pedal in cold weather, to open throttle valve 22. In cold weather,the conventional fast idle cam, not shown, would be engaged to maintainthe throttle valve open a predetermined angle, not shown. This assures asufficient air/fuel mixture to the engine upon cranking to overcome thefrictional resistance of the engine to start it and maintain it running.As soon as it is running, manifold vacuum acting on port 80 reflected inchamber 50 moves the diaphragm 46 rightwardly until spring 76essentially bottoms out. Altemately, a stop can be located in chamber 50projecting from shell 44. The dashpot assembly also moves rightwardly,the spring 68 maintaining piston extended until contact is made withthrottle valve lever 38. No further outward movement of piston 66 thenwill occur at this time.

The position of piston 66 will depend upon the condition of operation ofthe engine. If the fast idle cam is engaged for a cold weather start,the throttle valve will probably be in a position more like 36, forexample. In this case, piston 66 would probably be fully extended. Innormal operation, however, when the engine is warm, the spring 68 behindpiston 66 will be fully collapsed by the throttle retum spring 40 movingthe throttle valve lever 38 towards closed position. The vacuum forceacting on the disphragm 46, however, is sufficient to cause rightwardmovement of the collapsed dashpot assembly as a unit to position lever38 and throttle valve 22 in the idle speed position 36.

The vacuum force acting on the idle air/fuel discharge port 30 and thatpart of transfer port 28 below the edges of the throttle valve will drawfuel and air sufficient to maintain the desired engine idling speed.

Subsequently, when throttle valve 22 and lever 38 are rotated clockwisetowards a wide open position, for engine acceleration, the spring 68will now fully extend piston 66. Therefore, when the acceleration phaseis completed, and the vehicle accelerator pedal released, return spring40 will attempt to quickly return throttle valve 22 to an idle speedposition 36. The following then occurs. First, the lever 38 engages theend of plunger 64 and attempts to move it leftwardly. Since the airbehind piston 66 in chamber 74 can only escape through the orifice 70,the piston will collapse the spring 68 only slowly, providing a dashpotaction to throttle closing movement of the lever 38.

During engine deceleration, a very high vacuum is developed in themanifold and provides a very high signal in the idle channel 26.However, with the dashpot action, the slowly closing throttle valvemaintains increased air flow past the throttle valve, thus decaying thestrong idle system signal, and decreasing idle system fuel flow. The airflow helps to dry out the manifold, better scavenge the cylinder ofexhaust gases, and tends to maintain a more combustible mixture to thecylinder. Thus, the overall effect is to lessen the emission of unburnedhydrocarbons and carbon monoxides and other undesirable elements intothe atmosphere during deceleration operations.

Assume now the engine is shut down. Immediately, manifold vacuum inchamber 50 decays, permitting spring 76 to move diaphragm 46 and thedashpot assembly to the left to the positions shown. This permits thethrottle return spring 40 to rotate the lever 38 and throttle valve 22to the closed position 34. This pushes the plunger 64 to the positionshown, in which spring 68 is partially collapsed.

The closed position of the throttle valve thus reduces the vacuum signalarea on the idle channel to a level insuflicient to pull enough fuel/airmixture into the engine to support combustion. Dieseling thus isprevented.

While the invention has been described and illustrated in its preferredembodiment, it will be clear to those skilled in the arts to which itpertains that many changes and modifications may be made thereto withoutdeparting from the scope of the invention.

I claim:

1. A combination anti-dieseling and deceleration carburetor throttlevalve position control comprising, in combination, an engine carburetorhaving an induction passage open to essentially atmospheric pressure atone end and adapted to be connected to an engine intake manifold at theopposite end so as to be subject to engine vacuum varying in level fromambient atmospheric pressure at engine shutdown to a maximumsubatmospheric pressure level during engine deceleration operatingconditions, a throttle valve rotatably mounted across the passage andmovable from an essentially closed position to an engine idle speedposition and beyond to a wide open throttle position, and return, forcontrolling flow through said passage, and control means to move thethrottle valve to the various positions, the control means includingfirst means operatively biasing the throttle valve to a closed throttleantidiesel position, engine manifold vacuum sensitive means operableduring engine running to move the throttle valve to an open idle speedposition, and other means operable in response to deceleration operationslowly returning the throttle valve towards the idle position to delaythe return movement, the control means comprising a servo divided intoan atmospheric pressure chamber and a vacuum chamber by a flexiblediaphragm, and a plunger operably connected to the diaphragm andoperably engagable with the throttle valve to move or be moved by thethrottle valve, the other means comprising a dashpot including a sleevesealingly secured to the diaphragm and projecting through the servohousing, a piston slidable within the sleeve and having the plungersecured thereto, the piston havng an air. bleed port therein connectingopposite sides of the piston, and second spring means biasing the pistonand plunger towards the throttle valve.

2. A combination anti-dieseling and deceleration carburetor throttlevalve position control comprising, in combination, an engine carburetorhaving an induction passage open to atmospheric pressure at one end andadapted to be connected to an engine intake manifold at the opposite endso as to be subject to engine vacuum varying in level from ambientatmospheric pressure at engine shutdown to a maximum subatmosphericpressure level during engine deceleration operating conditions, athrottle valve rotatably mounted across the passage and movable from anessentially closed position to an engine idle speed position and beyondto a wide open throttle position, and return, for controlling flowthrough said passage, and control means to move the throttle valve tothe various positions, the control means including first meansoperatively biasing the throttle valve to a closed throttle anti-dieselposition, the control means comprising a vacuum controlled servo havinga shell divided into an atmospheric pressure chamber and a vacuumchamber by a flexible annular diaphragm, a sleeve sealingly secured atone end to the diaphragm in the vacuum chamber and projecting throughthe shell at the other end, a piston slidably and sealingly movablewithin the sleeve, a plunger fixed to the piston and projecting throughand guided by the end of the sleeve in a frictionally engaging mannerpermitting communication of air to the one side of the piston, thepiston having an orifice therein permitting the slow transfer of airfrom one side to the other delaying movement thereof during decelerationconditions, and second spring means biasing the piston and plungeroutwardly of the shell, the plunger being operably engagable with thethrottle valve whereby under no vacuum conditions at engine shutdown thethrottle valve is moved to a closed posiion by unitary return movementthereof with the piston and unitary movement of the sleeve anddisaphragm and piston by the first spring 1 means.

* l l i

1. A combination anti-dieseling and deceleration carburetor throttlevalve position control comprising, in combination, an engine carburetorhaving an induction passage open to essentially atmospheric pressure atone end and adapted to be connected to an engine intake manifold at theopposite end so as to be subject to engine vacuum varying in level fromambient atmospheric pressure at engine shutdown to a maximumsubatmospheric pressure level during engine deceleration operatingconditions, a throttle valve rotatably mounted across the passage andmovable from an essentially closed position to an engine idle speedposition and beyond to a wide open throttle position, and return, forcontrolling flow through said passage, and control means to move thethrottle valve to the various positions, the control means includingfirst means operatively biasing the throttle valve to a closed throttleanti-diesel position, engine manifold vacuum sensitive means operableduring engine running to move the throttle valve to an open idle speedposition, and other means operable in response to deceleration operaTionslowly returning the throttle valve towards the idle position to delaythe return movement, the control means comprising a servo divided intoan atmospheric pressure chamber and a vacuum chamber by a flexiblediaphragm, and a plunger operably connected to the diaphragm andoperably engagable with the throttle valve to move or be moved by thethrottle valve, the other means comprising a dashpot including a sleevesealingly secured to the diaphragm and projecting through the servohousing, a piston slidable within the sleeve and having the plungersecured thereto, the piston havng an air bleed port therein connectingopposite sides of the piston, and second spring means biasing the pistonand plunger towards the throttle valve.
 2. A combination anti-dieselingand deceleration carburetor throttle valve position control comprising,in combination, an engine carburetor having an induction passage open toatmospheric pressure at one end and adapted to be connected to an engineintake manifold at the opposite end so as to be subject to engine vacuumvarying in level from ambient atmospheric pressure at engine shutdown toa maximum subatmospheric pressure level during engine decelerationoperating conditions, a throttle valve rotatably mounted across thepassage and movable from an essentially closed position to an engineidle speed position and beyond to a wide open throttle position, andreturn, for controlling flow through said passage, and control means tomove the throttle valve to the various positions, the control meansincluding first means operatively biasing the throttle valve to a closedthrottle anti-diesel position, the control means comprising a vacuumcontrolled servo having a shell divided into an atmospheric pressurechamber and a vacuum chamber by a flexible annular diaphragm, a sleevesealingly secured at one end to the diaphragm in the vacuum chamber andprojecting through the shell at the other end, a piston slidably andsealingly movable within the sleeve, a plunger fixed to the piston andprojecting through and guided by the end of the sleeve in a frictionallyengaging manner permitting communication of air to the one side of thepiston, the piston having an orifice therein permitting the slowtransfer of air from one side to the other delaying movement thereofduring deceleration conditions, and second spring means biasing thepiston and plunger outwardly of the shell, the plunger being operablyengagable with the throttle valve whereby under no vacuum conditions atengine shutdown the throttle valve is moved to a closed posiion byunitary return movement thereof with the piston and unitary movement ofthe sleeve and disaphragm and piston by the first spring means.